Path_1 - Path 1 1. Increased lipolysis of fat stores, which...

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Path 1 1. Increased lipolysis of fat stores, which can result from starvation, diabetes mellitus, or corticosteroid use, is most likely to cause steatosis (fatty liver) through which one of the following mechanisms? A. Decreased free fatty acid excretion from the liver leads to free fatty acid accumulation in hepatocytes B. Excess NADH (high NADH/NAD ratio) causes excess production of lactate from pyruvate, which accumulates in hepatocytes C. Increased free fatty acid delivery to the liver leads to triglyceride accumulation in hepatocytes D. Inhibition of apoprotein synthesis by the liver leads to phospholipid accumulation in hepatocytes E. Inhibition of HMG-CoA reductase activity leads to cholesterol accumulation in hepatocytes The answer is: C Free fatty acids are normally taken up by the liver and esterified to triglyceride, converted to cholesterol, oxidized into ketone bodies, or incorporated into phospholipids that can be excreted from the liver as very-low-density lipoproteins (VLDLs). Abnormalities involving any of these normal metabolic pathways may lead to the accumulation of triglycerides within the hepatocytes. This accumulation of triglycerides is called fatty change or steatosis. Examples of abnormalities that produce hepatic steatosis include diseases that cause excess delivery of free fatty acids to the liver or diseases that cause impaired lipoprotein synthesis. Excess delivery of free fatty acids occurs in conditions that increase lipolysis of adipose tissue, such as starvation, diabetes mellitus, and corticosteroid use. Increased formation of triglycerides can result from alcohol use, as alcohol causes excess NADH formation (high NADH/NAD ratio), increases fatty acid synthesis, and decreases fatty acid oxidation. Impaired apoprotein synthesis occurs with carbon tetrachloride poisoning, phosphorous poisoning, and protein malnutrition. Inhibition of HMG-CoA reductase activity is the mechanism of lovastatin, which indirectly increases liver LDL receptors and increases LDL clearance from the blood. 2. An adult patient presents with the sudden onset of massive diarrhea. Grossly, this individual’s stool has the appearance of “rice-water” because of the presence of flecks of mucus. Cultures of this patient’s stool grow Vibrio cholerae, a curved, gram-negative rod that secretes an enterotoxin consisting of a toxic A subunit and a binding B subunit. The cholera enterotoxin causes massive diarrhea by which of the following mechanisms? A. Inhibiting the conversion of Gi-GDP to Gi-GTP B. Inhibiting the conversion of Gs-GTP to Gs-GDP C. Stimulating the conversion of Gi-GDP to Gi-GTP D. Stimulating the conversion of Gs-GDP to Gs-GTP E. Stimulating the conversion of Gs-GTP to Gs-GDP
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The answer is: B Many extracellular substances cause intracellular actions via second-messenger systems. These second messengers may bind to receptors that are located either on the surface of
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This note was uploaded on 11/21/2009 for the course BIO 1B taught by Professor Carlson,mischel,power during the Summer '07 term at Berkeley.

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Path_1 - Path 1 1. Increased lipolysis of fat stores, which...

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